Left atrial far-field sensing by left ventricular leads: a potential hazard in cardiac resynchronisation therapy

Cardiac resynchronisation therapy (CRT) requires a lead advanced through the coronary sinus (CS) to pace the left ventricle (LV). Left atrial far-field signals (LAFFS) may be sensed by the LV lead at the time of implant or after lead dislodgement, and may inhibit ventricular pacing.

To assess the incidence of detection of LAFFS > 2 mV and its correlation with the CS lead position.

Data from the first 75 consecutive patients enrolled in the InSync III multicentre study were analysed. The position of the LV lead was recorded at implant. During follow-up, pacing was temporarily inhibited and the LV channel electrogram was recorded. The amplitude of LAFFS observed before discharge from the hospital and at 1 month of follow-up was retrospectively analysed. A LAFFS > 2 mV was considered clinically significant.

CRT systems were successfully implanted in 71 of 75 patients. A LAFFS > 2 mV was recorded by the LV lead channel in six of 71 patients (8.5%). This phenomenon developed between hospital discharge and 1 month of follow-up in two of these patients and in one case disappeared within 1 month. It was observed in all CS tributaries except the anterior and mid-cardiac veins.

Left atrial far-field signals sensed by the LV lead were not rare. Implanting physicians should be aware of this phenomenon in order to prevent potentially serious complications.